Some people smell fear in potential business partners. Others smell a rat. But individuals who smell a certain brain hormone become unusually trusting of others in financial transactions, according to a new report.
Men who inhale a nasal spray spiked with oxytocin give more money to partners in a risky investment game than do men who sniff a spray containing no active ingredient, say economist Ernst Fehr of the University of Zurich and his colleagues.
Previous studies of nonhuman animals had suggested that oxytocin in the brain encourages long-term mating in pairs of adults and nurturing behaviors by mothers toward their offspring. This substance, which works as both a hormone and a neurotransmitter, fosters the trust needed for friendship, love, families, economic transactions, and political networks, Fehr proposes.
"Oxytocin specifically affects an individual's willingness to accept social risks arising through interpersonal interactions," he and his colleagues conclude in the June 2 Nature.
The scientists studied oxytocin's influence on male college students playing an investment game. Each of 58 men was paid $64 to participate in the experiment.
The volunteers were paired up, and one man in each pair was randomly assigned to play the role of an investor and the other to play the role of a trustee. Each participant received 12 tokens, valued at 32 cents each and redeemable at the end of the experiment.
The investor in each pair decided how many tokens to cede to the trustee. Both participants, sitting face to face, knew that the experimenters would quadruple that investment. The trustee then determined whether to keep the entire, enhanced pot or give some portion of the proceeds—whatever amount seemed fair—to the investor.
Among the investors who had inhaled oxytocin, about half gave all their tokens to trustees, and most of the rest contributed a majority of their tokens. In contrast, only one-fifth of investors who had inhaled a placebo spray forked over all their tokens, and another one-third parted with a majority of their tokens.
Oxytocin influenced only investors. Trustees returned comparable amounts of money after inhaling either spray. The trustee responses were generous when the investors offered most of their tokens and were stingy when the investment was small, Fehr and his coworkers report.
The influence of oxytocin was limited to social situations. In another part of the study, oxytocin didn't affect isolated investors who received randomly assigned amounts of money after making their contributions.
The oxytocin influence is "a remarkable finding," says neuroscientist Antonio Damasio of the University of Iowa College of Medicine in Iowa City in an editorial published with the new report. Damasio had previously argued that the hormone acts somewhat as a love potion. "It adds trust to the mix, for there is no love without trust," he says.
Worries may arise that crowds of people will be sprayed with oxytocin at political rallies or other events to induce trust in speakers, Damasio notes. However, he proposes that slick marketing strategies for political and other products probably already trigger oxytocin release in many consumers.
Fehr's group plans to determine what brain networks participate in oxytocin-inspired trust decisions and to consider whether oxytocin might counter social phobia and other mental disorders that result in social avoidance.
Department of Neurology
University of Iowa
College of Medicine
200 Hawkins Drive
Iowa City, IA 52242
University of Zurich
Institute for Empirical Research in Economics
A version of this article written for younger readers is available at Science News for Kids.